Although the invention is generally applicable to all types of cutting tools (e.g. milling, turning and drilling tools), the same has its origin in problems which are especially tied to milling cutters, in particular slitting cutters, having small cutting inserts.
In U.S. Pat. No. 5,800,079, a slitting cutter is disclosed, which in the traditional way includes a circular disc, the periphery of which is equipped with a plurality of replaceable cutting inserts of a hard and wear-resistant material, e.g., cemented carbide. These cutting inserts are mounted in separate cassettes of steel or the like, which are semi-permanently connected with the disc and placed in peripherally spaced-apart chip pockets, and can be exchanged individually if damage would occur, i.e., without the disc in its entirety needing to be discarded. In order to hold the individual cassette reliably anchored in the disc, as well as enable fine adjustment of the position of the cassette laterally, a wedge tightenable by a screw is used, by which a so-called serration surface (in the form of straight and parallel ridges and grooves) of the underside of the cassette can be forcefully pressed into a co-operating serration surface of the individual chip pocket of the disc. More precisely, the cross-sectionally wedge-shaped ridges of one of the serration surfaces is pressed into the grooves of the other serration surface, and vice versa, while providing a highly stable joint between the cassette and the disc, at the same time as the lateral position of the cassette, and thereby of the cutting insert, can be fine-adjusted in a simple way before the cassette is finally fixed by the wedge. The cutting insert is in turn mountable in a so-called insert seat or seating in the upperside of the cassette. In the tool that is shown in U.S. Pat. No. 5,800,079, the seating is delimited by a plane bottom surface or base surface, as well as two plane support surfaces, orientated perpendicularly to each other, viz. a rear support surface and a side support surface, against which surfaces the clearance surface of the cutting insert can be pressed by a compliant tightening screw, which simultaneously presses the underside of the cutting insert against the base surface of the seating. Later on, this tool was further developed so far that the base surface of the seating and the underside of the cutting insert were formed with coupling sections in the form of serration surfaces of the same type as of the joint between the underside of the cassette and the chip pocket of the disc, i.e., surfaces having mutually parallel ridges and grooves, which alternately engage each other. More precisely, the cutting insert was formed with a set of ridges, which extend parallel to two side clearance surfaces between front and rear ends, at least the front one of which includes the cutting edge requisite for the chip removal, while the base surface of the seating was formed with ridges, which extend in the plane of the disc (i.e., perpendicularly to the center axis of the disc), viz. from a front or outer end of the base surface toward the rear support surface. In such a way, the particular side support surface could be spared and the manufacture of the tool be facilitated.
The interface between the cutting insert and the cassette formed with two co-operating serration surfaces or coupling sections in the known side and face milling cutter works in a meritorious way as long as the cutting inserts are reasonably large, but if the cutting inserts have to be made with limited dimensions, problems occur so far that the ridges and the grooves of the coupling section of the cassette cannot be given sufficiently a great length to efficiently counteract rotation of the cutting insert and ensure a stable fixation of the same. Thus, the coupling section of the cassette is in practice manufactured by milling using a shank-end mill, by which a desired number of grooves are milled out in the initially plane base surface of the seating of the cassette. However, if the base surface of the seating is small in relation to the milling cutter, only short grooves and ridges can be provided. Supposing that the smallest shank-end mill, which can be used, has a diameter, which is as great as the length of the base surface, the length of the grooves and of the ridges is maximized to at most half of the diameter, because otherwise, the milling cutter would need to be fed forward so far that the same damages the protruding support surface.
The present invention aims at obviating the above-mentioned problems and at providing an improved tool for chip removing machining, in particular a side and face milling cutter. Therefore, an object of the invention is to provide a tool in which the seating or seatings, which has or have the purpose of receiving replaceable cutting inserts, can be formed with base surfaces, the coupling sections of which have an optimum projection area and the ridges a considerable length. In other words, it should be possible to form also small seatings for small cutting inserts with a base surface, which to the major extent is a coupling section of alternating ridges and grooves, wherein it should be possible to mill the grooves without damaging the protruding support surface of the seating, all for the purpose of ensuring a stable fixation of the cutting inserts and thereby a good machining precision.
Another object of the invention is to provide a tool, which is structurally simple and inexpensive to manufacture.